diff --git a/src/slic3r/GUI/OpenGLManager.cpp b/src/slic3r/GUI/OpenGLManager.cpp
index 83c4275f0..bdb005b1e 100644
--- a/src/slic3r/GUI/OpenGLManager.cpp
+++ b/src/slic3r/GUI/OpenGLManager.cpp
@@ -12,6 +12,7 @@
 #include <boost/log/trivial.hpp>
 
 #include <wx/glcanvas.h>
+#include <wx/msgdlg.h>
 
 #if ENABLE_HACK_CLOSING_ON_OSX_10_9_5
 #ifdef __APPLE__
diff --git a/src/slic3r/GUI/OpenGLManager.hpp b/src/slic3r/GUI/OpenGLManager.hpp
index 06bab2c14..9d7ee5bab 100644
--- a/src/slic3r/GUI/OpenGLManager.hpp
+++ b/src/slic3r/GUI/OpenGLManager.hpp
@@ -1,6 +1,7 @@
 #ifndef slic3r_OpenGLManager_hpp_
 #define slic3r_OpenGLManager_hpp_
 
+class wxWindow;
 class wxGLCanvas;
 class wxGLContext;